A solid-state imaging device that is represented by a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary Metal Oxide Semiconductor) image sensor includes a photoelectric conversion unit that is configured by a photodiode formed on the light receiving face side of a substrate and a charge transfer unit. In such a solid-state imaging device, light incident from the light receiving face side is photoelectrically converted by the photodiode so as to generate signal charge according to the amount of light. Then, the generated signal charge is transferred to a charge transfer unit and is output as a video signal.
In such a device, since a structure is employed in which light incident during an exposure time as a constant time interval is photoelectrically converted and accumulated, it is necessary for the photodiode to be open to the light receiving face side. Accordingly, in a case where an electrode is formed in an area that covers the light receiving face side of the photodiode, it is necessary for the electrode to be formed not from a general electrode material having a light shielding property but from a transparent electrode material.
As disclosed in JP-A-08-294059 and JP-A-07-94699, indium tin oxide (ITO) is mainly used as the material of a general transparent electrode in the related art. In addition, as disclosed in JP-A-2011-17819, in an electronic apparatus represented by a camera or the like, there is an example in which a light control element such as an electrochromic layer is used in an imaging optical system such as an aperture diaphragm or a shutter device. Even in such a case, as the material of a transparent electrode used for applying a desired electric potential to the electrochromic layer, ITO is used. However, ITO that is used as the material of the transparent electrode has low transmittance in the current status, and there are problems in that the sensitivity is decreased, and the optical characteristics change due to a large film thickness.